Excessive current within an electric machine may damage electrical components and/or demagnetise any permanent magnets. Accordingly, electric machines typically include an arrangement that prevents current in the electric machine from exceeding a threshold. One such arrangement involves a current sensor that outputs a voltage that is sensitive to current in the electric machine. A current controller then interrupts power to the electric machine in the event that the voltage output by the current sensor exceeds a threshold. However, owing to component tolerances in the current sensor and the current controller, there is a variance in the current at which the current controller interrupts the power. The current controller therefore interrupts power when the current in the electric machine reaches a level below that of the threshold. This then ensures that, in a worst case tolerance condition, the current in the electric machine does not exceed the threshold. However, in interrupting power at a current level below the threshold, the torque of the electric machine is compromised.